Cabinet-type adjustable and tunable indoor dipole antenna system



May 9, 1961 M. SPIRT 2,983,917

CABINET-TYPE ADJUSTABLE AND TUNABLE INDOOR DIPOLE ANTENNA SYSTEM FiledMay 19, 1958 2 Sheets-Sheet 1 FIG.I J0 0 17 I00 I50 20 250 o 0 49 0 Z 7""U m2 INVENTOR. M/z raw JP/er FIG.3

BY WM May 9, 1961 M. SPIRT 2,983,917

CABINET-TYPE ADJUSTABLE AND TUNABLE INDOOR DIPOLE ANTENNA SYSTEM FiledMay 19, 1958 2 Sheets-Sheet 2 6L 5 war 0 M INV EN TOR. Mm ro/v SP/eTAime/Va Patented May 9, 1961 CABINET-TYPE ADJUSTABLE AND TUNABLE INDOORDIPOLE ANTENNA SYSTEM Milton Spirt, P.O. Box 411, Jamaica, N.Y.

Filed May 19, 1958, Ser. No. 736,158

3 Claims. (Cl. 343-745) I ance matching stub for the dipole elements, awave trap inductor, an adjustable trimmer capacitor and a manuallyoperable multi-position switch for selecting various circuitcombinations of the several circuit elements and the .dipole elements,for connection to the receiver.

An object of the invention is to provide an antenna housed in a cabinetwhich may be placed on top of a television receiver or in a convenientadjacent location with the plane of the dipole elements continuouslyadjustable by means of the individual ball swivels through a full rangeof 360 degrees without moving the antenna cabinet.

A further object of the invention is the provision of a full complementof adjustable tuning elements for matching the antenna to the receiver,together with a manually operable switch for selecting the tuning elements in various combinations to obtain the best performance.

Various additional objects, features and advantages of the inventionwill become apparent upon reading the following specification togetherwith the accompanying drawings forming part thereof.

Referring to the drawings:

Fig. 1 is a front elevational view of an antenna embodying the inventionwith the dipole elements extended for use.

Fig. 2 is a plan View of the antenna of Fig. 1 showing the dipoleelements concealed within the cabinet when not in use.

Fig. 3 is a rear view in sectional elevation taken along the line 33 ofFig. 2, looking in the direction of the arrows.

Fig. 4 is an enlarged fragmentary sectional view in elevation showingdetails of construction of one of the ball swivel mountings for theantenna dipole elements.

Fig. 5 is a schematic circuit diagram of the antenna of Figs. 1 to 3.

Fig. 6 is a diagrammatic plan View of a manually operable multi-positionswitch for 'the selective control of switch'elements shown in Fig. 5.

Fig. 7 is a broken cross-sectional detail as on line 77 of Fig. 6.

Fig. 8 is an enlarged broken cross-sectional detail as on line 88 ofFig. 2.

Referring to Fig. 1, the antenna comprises a cabinet designatedgenerally as 10, and a pair of dipole elements individually designatedgenerally as 11 and 12,-respec tively. The cabinet 10 is formed ofelectrically insulative material. Each of the dipole elements 11 and 12is of conventional telescopic construction permitting its effectivelength to be individually adjusted to the optimum onequarter wave lengthvalue at the frequency of the signal which is being received.Ordinarily, a compromise intermediate length adjustment will givesatisfactory results. Generally, careful adjustment of dipole length isrequired only for unusually weak signals. The dipole elements 11 and 12are provided with enlarged tips 13 and 14, respectively, which may beconveniently grasped for pulling the dipole elements to withdraw themfrom the cabinet 10 or for extending their lengths after they have beenwithdrawn.

Each of the dipole elements 11 and 12 is longitudinally slidably mountedin an electrically conductive swivel ball 15 and 16, respectively. Eachdipole element is frictionally held against longitudinal movement in itsswivel ball as by a leaf spring 18, Fig. 4. The leaf spring .18 is bowedintermediate its ends at 19. The ends of the leaf spring 18 associatedwith dipole element 12 are secured against longitudinal and lateralmovement by being seated in a lateral recess 20 formed in the side ofthe central diametrical passage 22 in the wivel ball 14.

In the top wall of the cabinet 10 there is a circular aperture 23 havingbevelled edges 24 which engage a zone of the upper surface of the swivelball 14. At is periphery, the aperture 23 communicates with a verticallydownwardly extending slot 25 formed in the wall of cabinet 10. The lowerend of the slot 25 terminates in horizontal alignment with the center ofthe swivel ball 14 and thus permits the dipole element 12 to beswivelled into a horizontal position for longitudinal movement into orout of the cabinet 10. The other swivel'ball 15 is similarly arranged inall respects and does not need to be described in detail.

The ball 16 is received in the top of a vertically movable sleeve 27formed of electrically conductive material. At its upper end, the sleeve27 has a rounded edge 28 which engages the lower side of the ball 16. Anupright electrically conductive post 29 is slidably enclosed by thesleeve 27. The post 29 is mounted on a fixed sup porting bracket 30. Ahelical compression spring 32 surrounds the sleeve 27. The lower end ofthe spring 32 bears against the bracket 30 and its upper end pressesupwardly against the rounded edge '28 of the sleeve 27, thus supportingthe ball 16 and pressing it upwardly and firmly into frictionalengagement with the bevelled edge 24 of the circular aperture 23. At itslower end, the post 29 is provided with a terminal 33 to which aconductor 34 is connected. A conductor 35 is similarly arranged toprovide a connection to the other dipole element 11 through ball 15. Theouter end of the passage 22 in ball 16 is shown chamfered at 35 forreceiving the tapered base 36 of the tip member 14 when the dipoleelement 12 is fully inserted in the cabinet 10. Inward movement of thedipole elements 11 and 12 is limited by a depending stop wall 37 (Fig.3) integrally formed with the cabinet 10. Outward movement is limited bya collar 38 fixed to the inner end of dipole element 12 and which isreceived in a circular recess 39 formed in the swivel ball 16 as shovmin Fig. 4.

When extended, each dipole element is permitted by its associated swivelball to move throughout a conical zone having a vertical axis. Thus, thetwo dipole ele ments may be aligned in a common vertical plane directedtoward the transmitter from which a signal is to be received, regardlessof the position of the cabinet with respect to the transmitter.

A U-shaped impedance matching stub 41 disposed in a tubular housing 42is mounted within the cabinet 10. The stub 41 is provided with anadjustable shorting bar 43 which slidably engages and directlyinterconnects the parallel leg portions of the U-shaped stub 41. Theshorting bar 43 is secured to a longitudinally movable ring member 44.The tubular housing 42 has a longitudinally extending slot 45 formedtherein which permits the shorting bar 43 to be secured to thelongitudinally movable ring member 44. The front of the cabinet has a.horizontally extending slot 47 formed therein and adjustment knob 48 atthe front of the cabinet 10 is connected to the ring member 44 throughthe slot 47. The shorting bar 43 may be adjusted along the impedancematching stub 41 by horizontal displacement of the knob 48 at the frontof the cabinet 10. The knob 48 is provided with an index pointer 49which cooperates with a calibrated scale 50, so that the shorting bar 43may quickly be brought to any desired previously predetermined positionby reference to the pointer 49 and scale 50.

An adjustable trimmer capacitor 52 is disposed within the cabinet 10.The capacitor 52 is connected to an adjustment knob 53 by an inner shaft54 which is coaxial with an outer hollow shaft 56 journaled in bearingsupports 57a. The capacitor adjustment knob 53 is mounted exteriorly ofthe cabinet 10 in front of a switch control knob 57, the switch knob 57being fixed to the outer shaft 56.

A choke coil or wave trap inductor 58, Fig. 5, is also provided forconnection to the antenna circuit whenever desired.

There is a group of six single pole single throw control switches 61 to66 which permit the connection of the circuit elements 41, 52 and 58 tothe antenna conductors 34 and 35 in any desired combination by means ofcontrol cams 67 to 72 fixed to the hollow shaft 56.

Because of stray capacitance efifects, certain channels may be tunedmore sharply by connecting only a single terminal of one of the circuitelements 41, 52 and 58 to one of the antenna conductors 35 or 36. Thereis a total of 26 or 64 possible combinations of circuit connectionswhich may be established by the six switches 61 to 66. In practice,however, the effects of some of the sixty-four combinations may beduplicated by other combinations. Moreover, some of the switches may beomitted and be replaced by direct connections, thus further reducing thetotal number of switching combinations which are actually needed. In theembodiment illustrated in the drawing, only twelve switch positions areused. The positions of the knob 57 are numbered consecutively from 1 to12 and the desired switch position may be identified by reference tofixed index mark 74 on the front of the cabinet 10.

In operation, the two dipole antenna elements 11 and 12 are withdrawnfrom the cabinet 10 by grasping and pulling on the tips 13 and 14 untilthe collars 38 are seated in the recesses 39 in the swivel balls and 16.The antenna elements 1 1 and 12 are then elevated through the slots 25to their partially erect operating positions. Each of the dipoleelements may be individually moved in a conical zone which is limited bythe size of the circular apertures 23 in the top of the cabinet 10. Eachdipole element will be frictionally held in any desired position ofadjustment by the action of the compression springs 32. Phase reversalmay be easily effected by merely reversing the relative positions of thedipole elements 11 and 1 2. The most effective combination of circuitelements 41, 52 and 58 is selected by rotation of the switch controlknob 57. If the impedance matching stub 41 is connected for use, it maybe adjusted for optimum performance by horizontal movement of the knob48. If the trimmer capacitor 52 is connected for use, fine tuning may beeffected by means of the knob 53.

The operator will ascertain that a certain set of adjustments willproduce the best results for a particular channel and the antenna may bequickly adjusted to predetermined settings appropriate for each channel.In this manner, the need for a broadly tuned antenna system is avoidedand sharply selective adjustments may be used for each channel. Thissharp selectivity permits reception of distant stations and permits theindoor antenna of the present invention to be used in fringe areas withunusually excellent results.

While I have shown what I believe to be the best embodiment of myinvention, it will be apparent to those skilled in the art that variousmodifications may be made therein without departing from the spirit andscope of the invention as defined in the appended claims.

What is claimed is:

1. An antenna system comprising a pair of dipole antenna elements, acabinet in which said elements may be received when horizontallypositioned, individually adjustable supporting means in said cabinet,said elements being mounted in said supporting means, an antenna circuitconnected to said elements, an adjustable trimming capacitor in saidcabinet, a selector switch for selectively connecting said capacitor tosaid antenna circuit, two concentric knobs disposed exteriorly of saidcabinet, and two coaxial shafts individually connecting said knobs tosaid selector switch and to said capacitor.

2. An antenna system according to claim 1, further comprising anadjustable impedance matching stub connected to said antenna circuitthrough said selector switch, and a knob disposed exteriorly of saidcabinet and connected to said stub for adjusting the same.

3. A dipole antenna system for indoor use comprising a cabinet, saidcabinet having a pair of circular apertures formed in the topthereof, apair of swivel balls mounted in said cabinet, the upper portions of saidswivel balls engaging said circular apertures, a pair of fixed postseach disposed below the center of one of said swivel balls, an upwardlyspring pressed sleeve mounted on each post and each engaging the lowerportion of one of said swivel balls, a telescopic antenna elementslidably extending through the center of each swivel ball, frictionmeans carried by each swivel ball for retaining each antenna element inany desired position of longitudinal adjustment in its swivel ball, saidcabinet having downwardly extending slots formed therein each of whichcommunicates at one end with one of said circular apertures and whichterminates at its lower end in horizontal alignment with the center ofone of said swivel balls, each slot being adapted to receive one of saidantenna elements therein, and means defining a space within said cabinetfor receiving both of said antenna elements when said elements arehorizontally positioned and moved inwardly through said swivel balls andthe lower ends of said slots.

References Cited in the file of this patent UNITED STATES PATENTS2,558,487 Hills June 26, 1951 2,598,045 Fox et a1. May 27, 19522,810,909 Finkel Oct. 22, 1957 2,872,677 Whipple et al Feb. 3, 1959

